Date: Tue, 31 Oct 2017 13:39:38 +1100 From: "Tobin C. Harding" <me@...in.cc> To: Kees Cook <keescook@...omium.org> Cc: kernel test robot <xiaolong.ye@...el.com>, kernel-hardening@...ts.openwall.com, "Jason A. Donenfeld" <Jason@...c4.com>, Theodore Ts'o <tytso@....edu>, Linus Torvalds <torvalds@...ux-foundation.org>, Paolo Bonzini <pbonzini@...hat.com>, Tycho Andersen <tycho@...ker.com>, "Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, Jordan Glover <Golden_Miller83@...tonmail.ch>, Greg KH <gregkh@...uxfoundation.org>, Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>, Ian Campbell <ijc@...lion.org.uk>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <wilal.deacon@....com>, Steven Rostedt <rostedt@...dmis.org>, Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...org> Subject: Re: [lkp-robot] [printk] 7f7c60e066: BUG:KASAN:slab-out-of-bounds On Mon, Oct 30, 2017 at 05:14:59PM -0700, Kees Cook wrote: > On Wed, Oct 25, 2017 at 9:22 AM, kernel test robot > <xiaolong.ye@...el.com> wrote: thanks for looking at this, I was at a loss as to what (if any) action I needed to take. > > FYI, we noticed the following commit (built with gcc-4.9): > > > > commit: 7f7c60e0663645e757e520245606fde9c6e326bb ("printk: hash addresses printed with %p") > > url: https://github.com/0day-ci/linux/commits/Tobin-C-Harding/printk-hash-addresses-printed-with-p/20171024-231922 > > It's not clear to me which of the various versions this test ran > against, but it seems like the printf self-tests got very confused by > the results: > > > [ 40.275423] test_printf: kvasprintf(..., "%p %p", ...) returned '3cf9adbe eff717bf', expected '0000000001234567 fffffffffedcba98' > > [ 40.296739] test_printf: vsnprintf(buf, 256, "|%-*p|%*p|", ...) returned 19, expected 39 > > [ 40.322776] test_printf: vsnprintf(buf, 16, "|%-*p|%*p|", ...) returned 19, expected 39 > > [ 40.334834] test_printf: vsnprintf(buf, 0, "|%-*p|%*p|", ...) returned 19, expected 39 > > I assume v10 will fix the width issues, but probably not the value tests... Oh, so I need to update lib/test_printf.c to cover hashed %p. > And it claims a use-after-free, too: > > > [ 39.757461] The buggy address belongs to the object at 22cb34bb > > [ 39.757461] which belongs to the cache kmalloc-32 of size 32 > > [ 39.757461] The buggy address is located 0 bytes inside of > > [ 39.757461] 32-byte region [22cb34bb, 24ac3a60) > > Which becomes rather unreadable, since the address got hashed. :P So I think we need to patch mm/kasan/report to use %pK instead of %p. I don't know what I should be doing about [ 39.757461] BUG: KASAN: slab-out-of-bounds in __test+0xee/0x13f Awesome, thanks, Tobin.
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